Why is my "broken" engine getting better?
09-30-2011, 01:05 AM
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Why is my "broken" engine getting better?
So I had my engine compression tested about a month ago at a Mazda dealership and it turns out that rotor 2 was low. My car had been turbo'd and basically one of my spark plugs developed a small hairline crack which caused the car to misfire, and I obviously didn't catch the problem quick enough.
Anyway! I made the car completely stock again and upon taking the turbo off and starting it - the car was quite shakey at idle, slightly blue smoke from the exhaust, clearly down on power etc.
I decided to drive the car anyway since it wasn't all THAT bad to drive around in (and since I was needing a car anyway) and I was just planning on running it in the ground until I got a spare motor availble. The engine has turned out to be getting much more smooth at idle (although still a noticeable vibration), no smoke, and even the power is incredible strong at the top end but much less torque in lower RPM's than normal.
Why would the engine be getting better? It was seafoamed every year so I don't think it was just carbon build up, and it was almost undriveable at first.... but after about a month, I'm seriously contemplating if I should just save my money from getting another engine! (ohh and gas mileage is pretty damn normal as well)
Anyway! I made the car completely stock again and upon taking the turbo off and starting it - the car was quite shakey at idle, slightly blue smoke from the exhaust, clearly down on power etc.
I decided to drive the car anyway since it wasn't all THAT bad to drive around in (and since I was needing a car anyway) and I was just planning on running it in the ground until I got a spare motor availble. The engine has turned out to be getting much more smooth at idle (although still a noticeable vibration), no smoke, and even the power is incredible strong at the top end but much less torque in lower RPM's than normal.
Why would the engine be getting better? It was seafoamed every year so I don't think it was just carbon build up, and it was almost undriveable at first.... but after about a month, I'm seriously contemplating if I should just save my money from getting another engine! (ohh and gas mileage is pretty damn normal as well)
Last edited by BlackStealth; 09-30-2011 at 01:09 AM.
09-30-2011, 01:45 AM
#3
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but i would def still set money aside for either a rebuild or a new motor.
That's what i am doing right now.
Just going to ride current engine until it gives then rebuild it.
That's what i am doing right now.
Just going to ride current engine until it gives then rebuild it.
09-30-2011, 06:39 AM
#4
If it was running really rich the fuel can dilute the already poor compression and make it worse. After the chamber seals up a bit from more oil and less fuel your compression could get better
The high rpm thing is normal....poor rngine compression doesn't matter nuck after about 4K rpm because the dynamic compression goes up enough to run fine
You can run an engine without apex seals if you can get it started and keep the RPM's up high enough
I drove a couple of cars home with almost no compression after the seals went...just had to pull start the car and keep it moving
The high rpm thing is normal....poor rngine compression doesn't matter nuck after about 4K rpm because the dynamic compression goes up enough to run fine
You can run an engine without apex seals if you can get it started and keep the RPM's up high enough
I drove a couple of cars home with almost no compression after the seals went...just had to pull start the car and keep it moving
09-30-2011, 09:22 AM
#9
As stated that is the beautiful thing about the rotary. Last month I had a customer come in with a FD that had broken 2 seals on the apex seal where the apex seal tip meets the seal. and it ran and start just rough. The sad part is he bought the car that way.
While it will run and get you around for a bit I wouldn't push the motor too far.
When you get ready to rebuild your motor give me a call. Typical stock build: https://www.rx8club.com/rotary-inspired-performance-180/engine-rebuilds-219091/
While it will run and get you around for a bit I wouldn't push the motor too far.
When you get ready to rebuild your motor give me a call. Typical stock build: https://www.rx8club.com/rotary-inspired-performance-180/engine-rebuilds-219091/
09-30-2011, 11:04 AM
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I still don't understand what's happening inside the engine that is making it as good as it is...
To put things in perspective, it was not driveable at all! It was very difficult to start, and sounded horrible. I bet most people wouldn't be able to tell the difference from a well working engine aside from a bit more vibration at idle. It starts right up, and there's no stalling, or even a hestiation in my mind that I could drive it for several thousand miles or more without problems with the way it feel now! haha
To put things in perspective, it was not driveable at all! It was very difficult to start, and sounded horrible. I bet most people wouldn't be able to tell the difference from a well working engine aside from a bit more vibration at idle. It starts right up, and there's no stalling, or even a hestiation in my mind that I could drive it for several thousand miles or more without problems with the way it feel now! haha
09-30-2011, 11:12 AM
#11
I still don't understand what's happening inside the engine that is making it as good as it is...
To put things in perspective, it was not driveable at all! It was very difficult to start, and sounded horrible. I bet most people wouldn't be able to tell the difference from a well working engine aside from a bit more vibration at idle. It starts right up, and there's no stalling, or even a hestiation in my mind that I could drive it for several thousand miles or more without problems with the way it feel now! haha
To put things in perspective, it was not driveable at all! It was very difficult to start, and sounded horrible. I bet most people wouldn't be able to tell the difference from a well working engine aside from a bit more vibration at idle. It starts right up, and there's no stalling, or even a hestiation in my mind that I could drive it for several thousand miles or more without problems with the way it feel now! haha
As stated above by dannobre. You compression may have increased as the car has leaned out. You could have simply had a stuck seal that's freed up. You might just be lucky as hell.
You're still sitting on a ticking time bomb though.
Last edited by fuztupnz; 09-30-2011 at 11:14 AM.
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